(a) Field of the Invention
The present invention relates to a moving picture experts group (MPEG) data frame and a transmit and receive (Tx/Rx) system using the MPEG data frame. More specifically, the present invention relates to a digital TV broadcasting data frame for enhancing the receiving performance of a moving or fixed receiver, a digital TV Tx/Rx apparatus, and an MPEG data Tx/Rx system.
(b) Description of the Related Art
In general, digital TV provides higher resolution and has a wider screen than analog TV, and it provides multi-channel CD level audio sound. A change brought about by digital TV is the trend of regarding such devices not as home appliances but as a collection of services that will enhance levels of various services and their related techniques. The digital TV will generate other added values as much as the tremendous spreading of personal computers (PC) and the Internet, and will also likely influence overall industries such as information technology (IT), industrial techniques, and home appliances markets.
The U.S., Europe, and Japan each provide broadcasting methods, specifications and drive standardization for digital TV. In the case of the U.S., the transmission format adopted is the vestigial side band (VSB) method proposed by the U.S. company Zenith, the video compression format adopted is MPEG, the audio compression format adopted is Dolby AC-3, and the display format is provided to be compatible with existing display methods. Here, when an amplitude modulation on signals is performed, two side bands are generated, one on and one below a carrier wave. One side band signal is then greatly attenuated, and the other is modulated. This method is called VSB modulation. That is, since the double side band that uses upper and lower side bands has lower band efficiency, the single side band (SSB) that uses one side band is introduced, and this SSB is developed to VSB through filter implementation.
The Grand Alliance (GA) for unification of digital TV standards adopted 8 VSB as a broadcasting transmission method using terrestrial waves, and after that, the Advisory Committee on Advanced Television Service (ACATS) of the FCC also adopted 8 VSB as the transmission method for broadcasting terrestrial waves. Here, 8 VSB represents a signal allocation and transmission method wherein there are four data levels (+1, +3, +5, and +7) in the positive number side and another four data levels (xe2x88x921, xe2x88x923, xe2x88x925, and xe2x88x927) in the negative number side with reference to xe2x80x980xe2x80x99, thereby supplying eight transmitting signal levels. Therefore, when the terrestrial wave broadcasting station modulates digital data into 8 VSB format data and transmits the data to the air via an antenna, the digital TV at each house receives and demodulates the data in order for viewers to watch TV.
The above-noted terrestrial digital TV broadcasting system transmits a training signal every 24.2 ms in order for the receiver to adjust degradations generated by the transmission channels. However, since variations in multi-path characteristics and Doppler interferences exist within the 24.2 ms period, the receiver cannot accurately equalize the data. For this reason, some experts point out the weaknesses that it is more difficult to receive digital TV broadcasting programs by using an indoor antenna than to receive analog TV broadcasting programs, and it is impossible to receive digital broadcasting programs with a moving receiver in America.
The MPEG transport encoder that compresses the signals inserts 5 to 10% null packets into the total transmission data so as to adjust a target bit rate.
FIG. 1 shows a block diagram of a general VSB digital terrestrial broadcasting transmitter.
Referring to FIG. 1, a data randomizer 11 randomizes the data then outputs the randomized data to a Reed-Solomon (RS) encoder 12, the RS encoder 12 performs RS encoding on the random input data to add 20-byte parity codes and then outputs the data to a data interleaver 13. The data interleaver 13 interleaves the data according to a predetermined rule and outputs the interleaved data to an 8 VSB encoder (a trellis encoder 14 in this case). The trellis encoder 14 converts the interleaved data from byte-unit data into symbol-unit data, performs trellis encoding on the converted data and outputs the data to a multiplexer 15. The multiplexer 15 multiplexes trellis-encoded symbol sequences, segment sync signals provided from the outside, and field sync signals. The pilot inserter 16 inserts pilot signals into the multiplexed symbol sequences. The symbol sequences with the inserted pilot signals pass through a pre-equalizer filter 17 (this can be omitted) and then are provided to a VSB modulator 18. The VSB modulator 18 modulates the symbol sequences into VSB signals and outputs the VSB signals to a radio frequency (RF) upconverter 19. The RF upconverter 19 converts the modulated 8 VSB signals of a base band into RF band signals and transmits the converted data to the air via the antenna.
As shown in FIG. 1, the MPEG transport system inputs data to the digital terrestrial broadcasting transmitter. The data have a format in which a packet is configured as an MPEG2 transport stream (TS) of 188 bytes. The input data have a speed of 19.39 Mbps and a serial data format.
The input data are converted into a random format by the data randomizer, and RS encoding for adding 20-byte RS parity to a predetermined unit packet is performed, and then forward error correction (FEC) for 1/6 data field interleaving and trellis encoding at a 2/3 ratio is performed on the input data. The randomization and FEC processes are not performed on sync bytes of the transport packets. After the randomization and FEC processes, the data packets are converted into transmission data frames, and then data sync signals provided from the outside and the field sync signals are added.
FIG. 2 shows a configuration of a conventional transmission frame, and FIG. 3 shows a configuration of one field sync.
Referring to FIGS. 2 and 3, each data frame includes two data fields, and each field includes 313 data segments. The first data segment in the data field represents a data field sync signal, hereinafter referred to as a sync signal. This signal includes a training data sequence to be used by the receiver in the synchronization process.
The other 312 data segments respectively have a 188-byte transport packet and additional 20-byte data for the FEC. In actuality, the data in each data segment are generated from some transmission packets because of the data interleaving. The data segments include 832 symbols. The first four symbols are transmitted in a binary format and provide segment synchronization.
The data segment sync signal represents a sync byte that is the first of 188 bytes of the MPEG2 TS. The other 828 symbols represent 187 bytes of the transport packet and 20 bytes of the FEC. Since the 828 symbols are transmitted as 8-level signals, each symbol carries 3 bits. Therefore, 2484-bit (828xc3x973) data are transmitted in each data segment.
FIG. 4 shows a block diagram of a general receiver of a system for transmitting VSB terrestrial broadcasting.
Referring to FIG. 4, a tuner 21 selects a channel, an intermediate frequency (IF) filter 22 performs intermediate band filtering, and a sync frequency detector 22-detects desired frequencies. A sync and timing detector 22xe2x80x2 detects the sync signals and clock signals. When these signals are passed through an NTSC interference-rejection filter 23, an equalizer 24 removes interference caused by multi-path signals. A phase tracker 25 compensates for phase errors. The following channel decoder part is arranged in the reverse order to that of the transmitter.
As shown in FIGS. 1 to 4, since the first segment of the 313 segments of the general digital TV broadcasting data frames is configured as 2-level training sequences (field syncs) for equalizer convergence, when equalizing the channel equalizer of the receiver by only using the field sync of the first segment in the 8 VSB system, receiving the signals while moving is impossible.
To attempt to solve this problem, a blind equalization method to equalize the equalizer of the information data of the 312 segments excepting the 2-level training sequences is used, but in this blind equalization method, receiving performance is not fully improved when the receiver is moving since this method uses 8-level general information data.
It is an object of the present invention to provide digital TV broadcasting data frames wherein null packets are substituted with training data to use in the equalization process at the receiver and to improve receiving performance of multi-path signals in a fixed or moving condition when receiving digital TV broadcasting programs.
It is another object of the present invention to provide a digital TV transmitter for outputting digital TV broadcasting data frames.
It is still another object of the present invention to provide a digital TV receiver for receiving the digital TV broadcasting data frames.
It is still another object of the present invention to provide an MPEG data transmit/receive system for compensating for degradations generated in the transmission channel when transmitting and receiving the MPEG data.
In one aspect of the present invention, in a digital television broadcasting transmitting and receiving method using a data frame including at least one data field having 313 data segments, the first data segment of the data field being a data field sync signal including a training data sequence used in equalization by a receiver, and the remaining 312 data segments each including a 188-byte transport packet and 20-byte error correction data, a digital television broadcasting transmitting and receiving method using moving picture to experts group (MPEG) data frames comprises segments, corresponding to null packets from the 312 data segments, including a training sync signal that is a predetermined data pattern with a predetermined level, the training sync signal being used as training data for an equalizer at a receiver so as to increase receiving performance at a receiver that either moves or is stationary.
In another aspect of the present invention, in a digital television transmitter including a moving picture experts group 2 (MPEG-2) transport encoder that outputs serial data configured in a MPEG-2 transport stream configuration having 188-byte packets, and a data format buffer that temporarily stores the serial data and outputs formatted data, a digital television transmitter comprises a null packet detector for checking whether the formatted data include the null packets, and when the formatted data include the null packets, outputting skip pulses and training sync signals; an encoder for encoding the formatted data and outputting the encoded data, and when the skip pulses are input, freezing the encoding operation; and a multiplexer for receiving segment sync signals and data field sync signals provided from the outside, receiving the training sync signals from the null packet detector, multiplexing the encoded data provided by the encoder, and outputting digital television broadcasting data frames.
The encoder comprises: a data randomizer for randomizing the data provided by the data format buffer and outputting the randomized data, and when the skip pulses are input, freezing the randomizing operation; a Reed-Solomon (RS) encoder for performing RS encoding on the data output from the data randomizer and outputting the RS-encoded data, and when the skip pulses are input, freezing the RS encoding operation; a data interleaver for interleaving the RS-encoded data and outputting the interleaved data, and when the skip pulses are input, freezing the interleaving operation; and a trellis encoder for performing trellis encoding on the interleaved data and outputting the trellis-encoded data to the multiplexer, and when the skip pulses are input, freezing the trellis encoding operation.
The digital television broadcasting data frame comprises: a data frame including at least one data field having 313 data segments, the first data segment of the data field being a data field sync signal including a training data sequence used for equalization by a receiver, and the remaining 312 data segments each including a 188-byte transport packet and 20-byte error correction data; and segments, corresponding to null packets from the 312 data segments, including a training sync signal that is a predetermined data pattern with a predetermined level.